Current automotive catalytic converter devices comprise a multichannel substrate having flow-through channels which are coated with noble metal catalyst materials that convert the pollutant exhaust gases to harmless effluent.
The automotive catalytic converters generally comprise a large, oval-shaped ceramic substrate housed in a metal sleeve or can. The converters connect directly to a manifold exhaust pipe and normally discharge the purified gases into a muffler.
Exhaust gases entering the catalytic converter unit from the manifold exhaust pipe are usually quite specifically directed in their flow. The gas flow tends to concentrate in the middle portion of the ceramic substrate, thus substantially avoiding the outer one-third of the substrate. This is a result of the narrow exhaust pipe cross-section that feeds directly into the larger cross-sectional area of the substrate. The gases from the smaller exhaust pipe do not have a chance to radially diffuse as they enter the converter; thus, most of the exhaust gases flow down the middle of the substrate.
The result of this non-uniform bathing of the converter substrate is that, not only is the converter inefficient, but its operational life is also limited.
It is common with some catalytic converter systems that air is injected into the longitudinal mid-portion thereof in order to reduce the oxides of nitrogen emissions that are present in the exhaust gases. This procedure is also an inefficient use of converter substrate, since only a downstream portion of the substrate is provided with the oxygen-enriched effluent.
The present invention provides an apparatus at the inlet of the converter that will more uniformly bathe the substrate with exhaust gases. The apparatus is designed to provide the uniform bathing in an efficient manner, so that back pressure and turbulence in the exhaust conduit are minimized. The apparatus has a simple, integral construction, making the device inexpensive to both fabricate and install.
The subject catalytic converter accessory of this invention uses a dynamic exhaust gas mixture to bathe the catalytic converter substrate. This dynamic exhaust gas mixture comprises a bifurcated flow, comprising a substantially linear mid-portion stream, which is surrounded by an outer, diffuse, swirling stream of gases. The accessory device comprises a diffuser-shaped shell which has a barrier plate disposed in a mid-portion thereof. The device is installed at the exhaust pipe/converter interface.
The invention at hand reduces both turbulence and back pressure in the exhaust gas flow in three ways:
(1) The exhaust gases in the exhaust conduit are split into a bifurcated flow stream, in which only an outer portion of the exhaust gas stream is caused to swirl. These swirling outer gases expand into the converter chamber, bathing the outer portions of the catalytic substrate. The remaining mid-portion of the exhaust stream bathes the center of the catalytic substrate. This mid-portion comprises the major portion of the gaseous stream. It is maintained in a substantially linear flow in order to reduce turbulence and back pressure in the overall flow stream; PA1 (2) The exhaust gases are caused to diffuse prior to their bifurcation, thus allowing for a more uniform dispersion as they enter the catalytic converter interface. The diffusion of the outer flow stream portion of the exhaust gas, along with its swirling and expanding action, creates a quite effective and uniform bathing of the outer portions of the catalytic substrate; and PA1 (3) The swirling action is caused by a barrier plate disposed at the interface between the diffuser and the catalytic chamber and takes the place of an injected gas stream which is common to other such swirl-making devices. This results in lesser amounts of the turbulence and back pressure that are routinely experienced with the exhaust stream injection method.